This invention relates to electrical connectors and more particularly to an improved connector for joining two conductors extending transversely to one another at different levels and which cross one another defining a node point.
Grounding grids are used in electrical power installations where large amounts of electrical current are used or distributed, including utility generating stations and substations, and heavy industrial installations, such as refineries, chemical plants and steel mills. Grounding grids function to quickly and effectively dissipate surges of fault current so as to limit the potential damage of equipment and protect personnel close to the equipment.
Grounding grids consist of a matrix or crossover network of unjacketed, standard copper cable conductors buried underground or embedded in concrete and connected to above ground equipment by copper leads and to driven ground rods of copper-clad steel. At each cross-over point of the conductors or node of the matrix, a connection has to be made that is mechanically and electrically sound and reliable.
There are in common usage, three readily identifiable methods of connecting the grid conductors. One method involves the use of exothermic welding by which the two conductors are placed in a graphite mode to weld them together. One of the problems with this method is the requirement for a large inventory of graphite molds of different sizes to handle all the different possible combinations of conductor sizes, since one mold handles only one unique combination. Another problem is that of poor welds caused by worn molds allowing the molten metal to flow out of the weld area. Yet another problem is the possibility of initiating such a connection when moisture is present in the mold. In such event, the moisture may be converted by the molten metal to bubbling steam which can cause expulsion of the metal from the top of the mold.
A second method of connecting the conductors is with the use of compression connectors. This method requires an assortment of dies and tools to be used in installing the connectors by a crimping operation. A worn die, an improperly sized die, or an improperly functioning tool can cause failure of a joint due to poor crimping. Also, since the connector is deformed around the conductor, it must be constructed of a material with sufficiently low yield strength. Furthermore, after the crimping operation, the material of the connector tends to spring back away from intimate contact with the conductor. Also, since the connector must be applied at a point remote from the ends of a conductor, the barrel of the connector must be open on one side to allow the conductor to enter the connector barrel before crimping. This weakens the design after crimping in its ability to maintain a good contact force.
A third method of connecting the conductors is through the use of bolted connectors. This general class of connectors relies specifically on the torque-tension relationship of threaded fasteners to produce a clamping force. This type also relies on the inherent strength of the bolt to resist yielding during its service life. The bolt must be properly torqued to provide the correct clamping force.